The zebralight UI is complex. They generally will turn on to the level last used. But if you press the button and hold, they ramp from low to mid to high. You can adjust the intensities of the mid and high levels. And somewhere in there are strobes and SOS modes, barely useful.

Mostly what I care about - when I hit the button, there is light. Fiat lux!

When I activate mine, i simply hold the button until I get to the mid level - great for reading at night. When caving, the high beam is frequently useful, as is the very lowest level. It is nice to have the variable levels and it is good to see that as a common feature.

There have been plenty of occasions where I have wanted all the light possible, and right away. And i am a fan of using adapted night vision as much as possible, with minimal artificial lighting - often none at all with a starry sky or moon out.